This invention relates to check valves of the type embodying flexible or displaceable vanes that are adapted to be moved away from the axis of the conduit or other passage with which they are intended to operate to permit substantially unimpeded flow of fluid through the conduit or other passage, hereinafter referred to as "passage," in one direction, referred to herein as the "forward direction," and to be moved toward the axis of the passage and into engagement with each other to prevent the flow of fluid in the passage in the opposite direction, referred to herein as the "reverse direction."
Valves of this general type are well known and have been extensively used for various purposes.
It has been proposed to construct such valves with vanes composed of rubber or other plastic or elastomeric material. Such valves are advantageous because they can be manufactured at reasonable cost and, when subjected to pressure in the reverse direction, are substantially free from leakage. However, usage of prior art valves of this general type has been severely restricted because the construction of the vanes is such that the valves are unable to withstand large back pressures without leakage or, if the vanes are made heavy enough to withstand such back pressures, then the forward pressure required to open the valves may become impermissibly large, with the result that the valves present substantial resistance to the flow of fluid through the conduit in the forward direction.
Prior art valves of the general type referred to are shown, for example, in the following U.S. patents:
U.S. Pat. No. 2,670,757--Mar. 2, 1954--Delany PA0 U.S. Pat. No. 2,822,819--Feb. 11, 1958--Geeraert PA0 U.S. Pat. No. 3,148,696--Sept. 15, 1964--Hoke PA0 U.S. Pat. No. 3,174,434--Mar. 23, 1965--Schieve PA0 U.S. Pat. No. 3,896,849--July 29, 1975--Ervin et al.
In service, valves of the type illustrated in these patents are subject to either or both of the disadvantages noted above.